My question is about using a plastic crown as a permanent solution for a cracked tooth. I have an upper left tooth (#26) that has had a root canal and recently cracked from the surface down into the root. The dentist has said that because the root is cracked they can’t put a post in, and because of that they can’t use a porcelain crown. So far he has cemented the crack, prepared the tooth, and taken imprints to make a plastic crown. He said the plastic crown should last about 5 to 10 years. Everything I’ve read only mentions plastic crowns for very short term use. Does this sound like a reasonable treatment?